Implantable analyte sensors offer a convenient and accurate alternative to analyte testing methods such as fingerstick blood glucose meters. Indwelling sensors also offer an additional advantage in that analyte concentrations in an individual may be tracked over a period of time without requiring the individual to draw a blood sample for each measurement. Where close attention to blood analyte concentrations is correlated with better outcomes, an indwelling analyte sensor may be superior to other monitoring options. In diabetes, for example, blood glucose levels that are either higher or lower than a target level may result in serious medical complications. Continuously monitoring blood glucose levels using an implanted sensor and an external electronic measuring device may improve the user's ability to control blood glucose levels, thus reducing the incidence and severity of such complications.
Flexible indwelling sensors may be more comfortable for the user than rigid or semi-rigid sensors, and less likely to experience failure due to mechanical stress induced by the user's movements. Flexible indwelling sensors have been described, for example, in U.S. Pat. No. 5,165,407 to Ward et al. However, the insertion of flexible sensors requires an initial piercing of the skin due to the tendency of flexible sensors to bend. Therefore, insertion of flexible sensors is often accomplished by inserting the sensor through a rigid hollow mechanism such as a needle, a cannula or a trocar used to create a channel through which the sensor could pass. See, for example, U.S. Pat. No. 6,695,860 to Ward et al.
The use of such piercing mechanisms for sensor insertion may cause physical and emotional discomfort among users, discouraging the use of indwelling sensors for continuous blood analyte monitoring. Piercing mechanisms that accommodate a sensor may be large and painful to insert through skin. In addition to the physical discomfort associated with piercing mechanisms, an individual in need of consistent blood analyte monitoring may be reluctant to use such a mechanism without assistance.
Analyte sensor flexibility reduces user discomfort in long-term sensor use. But as flexibility increases, the capacity of the sensor to directly penetrate unbroken skin diminishes. While flexible indwelling analyte sensors may improve a user's ability to monitor blood analyte levels for optimal medical outcomes, the available insertion methods may be unacceptable to some who are in need of monitoring.